Subscribe

Are aliens hard to find because they're extinct?

A new study suggests that aliens could have been common throughout the universe, but that evolution proved too difficult for most life to survive.

  • close
    Now-defunct radio telescopes of the Allen Telescope Array in Hat Creek, Calif, in 2007. Astronomers used the dishes to scan for alien signals.
    Ben Margot/AP/File
    View Caption
  • About video ads
    View Caption
of

Evidence of extraterrestrial life may be hard to find because alien species have all died out, a new study suggests.

Researchers Aditya Chopra and Charles Lineweaver, both of the Australian National University, recently published a paper in the journal Astrobiology suggesting that extinction could be the main cause of humanity’s fruitless search for extraterrestrials.

“The universe is probably filled with habitable planets, so many scientists think it should be teeming with aliens,” said Mr. Chopra in a release from the university. However, Chopra and Dr. Lineweaver say that, despite the presence of livable sites, alien life may not have evolved quickly or well enough to sustain itself on various worlds.

“Early life is fragile, so we believe it rarely evolves quickly enough to survive,” Chopra said. “Most early planetary environments are unstable. To produce a habitable planet, life forms need to regulate greenhouse gases such as water and carbon dioxide to keep surface temperatures stable.”

This conjecture, which Chopra and Lineweaver call a “Gaian bottleneck,” offers a different view on alien existence than previous similar ideas and provides an answer to the Fermi paradox – the conflict between the apparently high probability that alien life could evolve and the lack of any hard evidence demonstrating alien development.

The Gaian bottleneck conjecture submits that the overlap between a species' habitable conditions and its planet's actual conditions is usually very brief, and that most species die out before they can evolve or change their environment enough to match with both.

The new study also offers a different view on a concept first proposed by George Mason University economist Robin Hanson that suggests that science’s current perception of the process of basic evolution that eventually leads to intelligent life and cosmic colonization is wrong.

Prof. Hanson hypothesized that there is a step, which he calls the Great Filter, in the universal “evolutionary path” that almost no species can successfully complete. “[S]o far nothing among the billion trillion stars in our whole past universe," he writes, "has made it all the way along this path.” 

The Great Filter suggests that humanity may be doomed to be filtered out at some point in the future, but Chopra and Lineweaver’s study goes in a different direction in saying that early life is somewhat responsible for making its environment habitable and in a way providing for its own evolution - indicating that humanity already passed through its filter.

This idea means that in most instances where life has existed, it has died; “extinction is the cosmic default,” according to the researchers. It also means that if there was no life originally on a planet after its formation, it is very unlikely that place would ever see the presence of anything living; “planets need to be inhabited to remain habitable.” These two arguments are Chopra and Lineweaver’s answer to Fermi’s paradox and would explain why life is apparently so rare in the universe.

So it is possible that alien species existed all over the universe in environments conducive to life, but if humanity ever finds traces of them it’s likely to be in the form of fossilized, basic life forms that simply didn’t evolve rather than as evidence of sentient aliens with advanced civilizations.

“One intriguing prediction of the Gaian Bottleneck model is that the vast majority of fossils in the universe will be from extinct microbial life, not from multicellular species such as dinosaurs or humanoids that take billions of years to evolve,” said Lineweaver.

About these ads
Sponsored Content by LockerDome
 
 
Make a Difference
Inspired? Here are some ways to make a difference on this issue.
FREE Newsletters
Get the Monitor stories you care about delivered to your inbox.
 

We want to hear, did we miss an angle we should have covered? Should we come back to this topic? Or just give us a rating for this story. We want to hear from you.

Loading...

Loading...

Loading...

Save for later

Save
Cancel

Saved ( of items)

This item has been saved to read later from any device.
Access saved items through your user name at the top of the page.

View Saved Items

OK

Failed to save

You reached the limit of 20 saved items.
Please visit following link to manage you saved items.

View Saved Items

OK

Failed to save

You have already saved this item.

View Saved Items

OK